Transplantation of neuroblastic progenitor cells as a sheet preserves and restores retinal function

Diseases affecting the outer retina are incurable once photoreceptors are lost, and these diseases usually cause retinal pigment epithelium (RPE) dysfunction. However, the inner retina can remain functional for some time, even though retinal remodeling occurs as compensation for photoreceptor loss. If the damaged part can be replaced with neuroblastic progenitor and RPE cells as sheets with a beneficial effect on function, vision loss may be prevented and vision may be restored. This review presents an overview of the research of transplanting sheets of neural retina, with or without its RPE, to the subretinal space. In different animal models of retinal degeneration, retinal transplants can morphologically reconstruct a damaged retina, and restore visual sensitivity. Good morphological integration of transplants with the host retina can occur, whereas other transplants exhibit a glial barrier. Synaptic connections between transplant and host have been indicated by transsynaptic tracing. Retinal transplants can restore and preserve visual responses in a small area of the superior colliculus corresponding to the placement of the transplant in the retina. The beneficial effect of retinal transplantation likely involves two mechanisms: trophic effects, e.g., rescue of host cones; and synaptic connectivity between transplant and host retina.